Wide varieties of materials have been employed heretofore for parts and portions of installations and furnishings in the automobile, machinery, electric and electronic industries and architectural field requiring rubbery elasticity. Among them, vulcanized rubber may be exemplified. Vulcanized rubber is obtained usually through laborious and expensive process steps by first preparing an unvulcanized rubber blend by kneading raw rubber together with a cross linking agent, cross linking assistant, additives and subsidiary component(s) and then processing the resulting kneaded mass by vulcanization while forming it into a contemplated formed product under heating. Vulcanized rubber products have cross-linked molecular structure and, therefore, are not able to be recycled for reclamation.
On the other hand, polyvinyl chloride resin has a rubber-resembling property, though it does not require vulcanization step. However, polyvinyl chloride resin suffers from a significant problem of evolving a noxious gas upon incineration thereof. In addition, the rubbery elasticity thereof is inferior as compared with vulcanized rubber, so that the application field thereof is limited.
There have been known thermoplastic elastomers which behave at normal temperature as a polymer material exhibiting a rubbery elasticity but can be plasticized at a high temperature and, thus, can be processed by forming or molding into formed product. As concerns this, there has been known, as a thermoplastic elastomer based on olefin, a dynamically cross-linked product made of a polypropylene and an ethylene/.alpha.-olefin copolymer. However, this also suffers from similar problems as above due to incorporation of a dynamic cross linking step.